This invention relates primarily to a water based protective coating composition which is most particularly useful for undercoating of vehicles to prevent corrosion. As explained later herein, the composition may if desired, be modified to provide a solvent base system; however, it is most preferred that the composition be aqueous in order to eliminate some inherent problems in solvent based systems such as odor, potential flame hazards, and the like.
Generally in the metal coating industry, and particularly in the automobile undercoating industry, there is a continuing need for coatings which provide good corrosion resistance. An effective undercoating for metal substrates, particularly automobiles, should be one which upon drying provides a good, strong, tough film. Additionally, the film should have a high solids content which not only enhances corrosion resistance but also allows the film to provide some sound, or noise, insulation. Then too, a satisfactory film should be one which has good adherence properties to the underlying substrate. Finally, a good undercoating composition should be one which is not only effective but economical to manufacture and one which is easy for a user to apply. With regard to ease of application, one problem which often occurs in spraying of undercoating compositions is that they will have a tendency to "overspray". Ideally, a good composition will have a narrow but effective spray pattern.
A primary object of this invention is to provide a butadiene styrene latex coating composition, particularly an aqueous composition, which achieves each of the above desirable attributes.
Another object of this invention is to provide a butadiene styrene latex coating composition using mica as a filling and flattening agent, and also employing a newly found advantage that if mica is employed as a filling and flattening agent, it also stabilizes the composition to prevent premature gelling.
A further object of this invention is to provide a product of enhanced anti-foaming properties. That is to say, foaming is undesirable and providing that ammonium hydroxide is used as a pH control agent to provide a pH within the range of 7.5 to 10.0, for reasons that are unknown, the ammonium hydroxide enhances the effectiveness of the defoaming agents employed.
Yet another object of this invention is to provide a method of manufacture of a latex, butadiene styrene car undercoating system.
An even further object of this invention is to provide a high solids content coating, even as high as 45-50%, for a solvent based butadiene styrene polymer system.
Yet another object of the invention is to provide a coating composition which upon drying provides a barrier to moisture which is effective because of overlapping platelets of mica.
The method and means of accomplishing these objectives, and others, will become apparent from the detailed description of the invention which follows.